Vicente Montiel

University of Alicante, Alicante, Valencia, Spain

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Publications (102)300.17 Total impact

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    ABSTRACT: In this study, we examine the performance of Cu 2 O and Cu 2 O/ZnO surfaces in a filter-press electro-chemical cell for the continuous electroreduction of CO 2 into methanol. The electrodes are prepared by airbrushing the metal particles onto a porous carbon paper and then are electrochemically characterized by cyclic voltammetry analyses. Particular emphasis is placed on evaluating and comparing the methanol production and Faradaic efficiencies at different loadings of Cu 2 O particles (0.5, 1 and 1.8 mg cm −2), Cu 2 O/ZnO weight ratios (1:0.5, 1:1 and 1:2) and electrolyte flow rates (1, 2 and 3 ml min −1 cm −2). The electrodes including ZnO in their catalytic surface were stable after 5 h, in contrast with Cu 2 O-deposited carbon papers that present strong deactivation with time. The maximum methanol formation rate and Faradaic efficiency for Cu 2 O/ZnO (1:1)-based electrodes, at an applied potential of −1.3 V vs. Ag/AgCl, were r = 3.17 × 10 −5 mol m −2 s −1 and FE = 17.7 %, respectively. Consequently, the use of Cu 2 O–ZnO mixtures may be of application for the continuous electrochemical formation of methanol, although further research is still required in order to develop highly active, selective and stable catalysts the electroreduction of CO 2 to methanol.
    Applied Catalysis B Environmental 05/2015; 176:709-717. DOI:10.1016/j.apcatb.2015.04.055
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    ABSTRACT: In this work, electrodialysis has been proved to be a suitable technique for decreasing the conductivity of a real wastewater from an almond industry, which has been previously treated by electrocoagulation (EC) and electrooxidation (EO). A seven-cell electrodialyzer, with total active membrane area of 1400 cm2, was employed and several parameters, as the limiting current density, were determined. A method for measuring voltage across the membranes was developed, in order to control membrane fouling. The method consisted of capillaries inserted into the solution compartments and connected to a high impedance voltmeter. A study of the reuse of the concentrate solution was made, and it was stated that it can be concentrated 10 times. The treatment of the wastewater was performed at different voltages (7-16 V) to reach values of conductivity of the diluate of 0.5 mS cm−1. After that, the scaling up to a pre-industrial scale was performed by using a 70-cell electrodialyzer, with total active membrane area of 3.5 m2. The process was performed by applying voltages of 20-70 V and a final conductivity of the diluate of 0.5 mS cm−1 was achieved. The electric energy consumption was calculated in every case.
    Journal of Membrane Science 02/2015; 476:580-589. DOI:10.1016/j.memsci.2014.11.007
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    ABSTRACT: Abstracts: * Aiche meeting abstract- Del Castillo.docx (15.4KB) - Uploading Abstracts
    14 AIChE Annual Meeting; 11/2014
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    ABSTRACT: Oxidative stress has recently became one of the most important and negative factors that affect favourable human reproduction and therefore plays a crucial role in the successful outcome rates on artificial reproduction techniques (ARTs). The effects of oxidative stress are strengthened in an ART setting since there are more sources of reactive oxygen and nitrogen species (ROS/RNS) generation and a more vulnerable physiological defence mechanism. Culture media, for this reason, have improved in their composition and are becoming more complex, above everything, in their antioxidant power to face ROS/RNS generation. In this work, we suggest the use of electrochemical (bio)sensors to evaluate the presence and evolution of nitric oxide (NO) and superoxide anion (O-2(-)), in a commercial culture medium compared to conventional phosphate buffer solution. The electrochemical monitoring of NO was followed by the real-time NO-release from a commercially available NO donor (diazeniumdiolate) under aerobic conditions in a surface-modified screen-printed linear platinum array electrode. Concurrently, superoxide anion detection was evaluated at a surface-modified screen-printed linear gold electrode by the real-time and in situ generation of O-2(-). The performances of both arrayed sensors were compared to-those obtained at single modified ultramicroelectrodes. We deepen the study of the intrinsic and external interferents for the application of these electrochemical (bio)sensors in order to provide an oxidative stress index during embryo development. (C) 2014 Published by Elsevier Ltd.
    Electrochimica Acta 09/2014; 140:42-48. DOI:10.1016/j.electacta.2014.03.012
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    ABSTRACT: Herein, we explore the immobilization of nickel on various carbon supports and their application as electrocatalysts for the oxidation of propargyl alcohol in alkaline medium. In comparison with massive and nanoparticulated nickel electrode systems, Ni-doped nanoporous carbons provided similar propargyl alcohol conversions for very low metallic contents. Nanoparticulated Ni on various carbon supports gave rise to the highest electrocatalytic activity in terms of product selectivity, with a clear dependence on Ni content. The results point to the importance of controlling the dispersion of the Ni phase within the carbon matrix for a full exploitation of the electroactive area of the metal. Additionally, a change in the mechanism of the propargyl alcohol electrooxidation was noted, which seems to be related to the physicochemical properties of the carbon support as well. Thus, the stereoselectivity of the electrooxidative reaction can be controlled by the active nickel content immobilized on the anode, with a preferential oxidation to (Z)-3-(2-propynoxy)-2-propenoic acid with high Ni-loading, and to propiolic acid with low loading of active Ni sites. Moreover, the formation of (E)-3-(2-propynoxy)-2-propenoic acid was discriminatory irrespective of the experimental conditions and Ni loadings on the carbon matrixes.
    Carbon 07/2014; 73:291–302. DOI:10.1016/j.carbon.2014.02.066
  • IX IBERO-AMERICAN CONGRESS ON MEMBRANE SCIENCE AND TECHNOLOGY, SANTANDER; 05/2014
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    ABSTRACT: IntroductionOne of the typical problems addressed in electrochemical textbooks is how to define the theoretical kinetic law of an electrochemical reaction and how to propose a plausible mechanism for this reaction from its kinetic parameters, usually the Tafel slope and reaction orders.Most electrochemical reactions consist of at least two electron transfers, and it is usually accepted that their probability of being multiple simultaneous electron transfers is low, i.e., only single-electron transfer reactions are possible (although it seems that a simultaneous two-electron transfer can occur in certain cases). Thus, for an n-electron transfer reaction such as ...
    03/2014; 6(2):148-154. DOI:10.1007/s12678-014-0236-8
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    ABSTRACT: The direct electron transfer of cytochrome c has been studied at screen-printed graphite macroelectrodes without recourse to mediators or the need for any electrode pre-treatment as is commonly employed within the literature. A wide range of pH values from 2.0 to 11.0 have been explored upon the electrochemical response of cytochrome c and different voltammetric signatures have been observed. The direct electron transfer of the alkaline transition of cytochrome c was found impeded within alkaline media leading to either an irreversible redox process or even no voltammetric responses. In acidic aqueous media the electrochemical process is observed to undergo a mixed diffusion and adsorption controlled process rather than a purely diffusional process of the native conformation as observed at pH 7.0. Interestingly, at pH 3.5 a new conformational state is revealed in cooperation with the native conformation. The immobilization of the protein was satisfactorily obtained using a simple method by cycling the protein at specific solution pH values allowing amperometric responses to be obtained and gives rise to useful pseudo-peroxidase activity for sensing H2O2. Apparent Michaelis-Menten constant values (Km) were calculated via the Lineweaver-Burk method with deduced values of 25 ± 4, 98 ± 12 and 230 ± 30 mM, respectively for pH values of 2.0, 3.0 and 7.0. Such work is important for those utilising cytochrome c in bio-electrochemical and related applications.
    The Analyst 02/2014; DOI:10.1039/c3an02137h
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    ABSTRACT: Food industries such as almond industry generate large volumes of wastewater in their processes and common techniques are not always efficient for treating this kind of effluents. In this work, the feasibility of a treatment for pollutants removal of a real industrial wastewater by electrochemical oxidations studied at laboratory scale and then scaled-up to pre-industrial scale. The first stage of the work was performed at laboratory scale, using a 63 cm2 cell, where different anodes (Ti/Pt, and DSA anodes (Ti/RuO2 and Ti/IrO2)) and the optimal experimental conditions (pH, current density, temperature and [Cl−]) were studied and established. By using a DSA-Cl2 anode (Ti/RuO2), pH 9, j = 50 mA cm−2, [Cl−] = 2000 mg L−1 and room temperature, chemical oxygen demand (COD) was removed up to 75% and results show that electrooxidation can remove organic pollutants. In the second stage the scaling-up of the process from laboratory to pre-industrial scale was performed, by using a 3300 cm2 cell. The electrochemical reactor was finally powered by a photovoltaic generator directly connected, in order to operate by using a renewable energy and a COD elimination of 80% was achieved.
    Separation and Purification Technology 02/2014; 123:15–22. DOI:10.1016/j.seppur.2013.12.023
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    ABSTRACT: The pre-pilot scale synthesis of 1-phenylethanol was carried out by the cathodic hydrogenation of acetophenone in a 100 cm2 (geometric area) Polymer Electrolyte Membrane Electrochemical Reactor. The cathode was a Pd/C electrode. Hydrogen oxidation on a gas diffusion electrode was chosen as anodic reaction in order to take advantage of the hydrogen evolved during the reduction. This hydrogen oxidation provides the protons needed for the synthesis. The synthesis performed with only a solid polymer electrolyte, spe, has lower fractional conversion although a higher selectivity than that carried out using a support-electrolyte-solvent together with a spe. However, the difference between these two cases is rather small and since the work-up and purification of the final product are much easier when only a spe is used, this last process was chosen for the pre-pilot electrochemical synthesis of 1-phenylethanol.
    Electrochemistry Communications 09/2013; 34:316-319. DOI:10.1016/j.elecom.2013.07.018
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    ABSTRACT: Arylated anthraquinone derivatives of different sizes and different π-basicities have been prepared, and the electrochemical behaviour of these substances has been studied on screen printed graphite electrodes in the three room temperature ionic liquids (RTILs), 1-butyl-3-methylimidazolium hexafluorophosphate ([C4MIM][PF6]), 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6MIM][PF6]) and 1-octyl-3-methylimidazolium hexafluorophosphate ([C8MIM][PF6]). Half redox potentials for the first and second one electron reduction waves were identified, and the diffusion coefficient values were estimated from cyclic voltammetry measurements. The influence of the nature of the RTIL and of the substitution pattern of the anthraquinone on the solvodynamic radii were studied. A correlation of the reductive potentials with the corresponding Hammett constants of the substituents was tested. Copyright © 2013 John Wiley & Sons, Ltd.
    Journal of Physical Organic Chemistry 04/2013; 26(4):367-375. DOI:10.1002/poc.3098
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    ABSTRACT: The use of a solid polymeric electrolyte, spe, is not commonly found in organic electrosynthesis despite its inherent advantages such as the possible elimination of the electrolyte entailing simpler purification processes, a smaller sized reactor and lower energetic costs. In order to test if it were possible to use a spe in industrial organic electrosynthesis, we studied the synthesis of 1-phenylethanol through the electrochemical hydrogenation of acetophenone using Pd/C 30 wt% with different loadings as cathode and a hydrogen gas diffusion anode. A Polymer Electrolyte Membrane Electrochemical Reactor, PEMER, with a fuel cell structure was chosen to carry out electrochemical reduction with a view to simplifying an industrial scale-up of the electrochemical process. We studied the influence of current density and cathode catalyst loading on this electroorganic synthesis. Selectivity for 1-phenylethanol was around 90% with only ethylbenzene and hydrogen detected as by-products.
    Electrochimica Acta 02/2013; 91:69–74. DOI:10.1016/j.electacta.2012.12.097
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    ABSTRACT: Nitration in proteins is a physiologically relevant process and the formation of 3-nitrotyrosine was first proposed as an in vivo marker of the production of reactive nitrogen species in oxidative stress. No studies have been published on structural changes associated with nitration of myoglobin. To address this deficiency the electrochemical nitration of equine skeletal muscle (Mb) at amino acid tyrosine 103 has been investigated for the evaluation and characterization of structural and thermal stability changes. Y103 in Mb is one of the most exposed tyrosine residues and it is also close to the heme group. Effects of Y103 nitration on the secondary and tertiary structure Y103 have been studied by UV-Vis, circular dichroism, fluorescence and NMR spectroscopy and by electrochemical studies. At physiological pH, subtle changes were observed involving slight loosening of the tertiary structure and conformational exchange processes. Thermal stability of the nitrated protein was found to be reduced by 5 °C for the nitrated Mb compared with the native Mb at physiological pH. Altogether, NMR data indicates that nitrated Mb has a very similar tertiary structure to that of native Mb, although with a slightly open conformation.
    Archives of Biochemistry and Biophysics 11/2012; 529(1). DOI:10.1016/j.abb.2012.10.013
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    ABSTRACT: Screen printed graphite electrodes (SPGEs) have been characterized in the room temperature ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate [C6MIM][PF6] by studying pertinent electrochemical parameters of the electroactive species ferrocene (Fc), 1,4-benzoquinone (BQ), 1,4-diphenyl-9,10-anthraquinone (AQ), tetracyclone (TC) and benzophenone-3 (BZ-3). Diffusion coefficients and kinetics calculations together with Digisim simulations for comparison were performed. Additionally, the reductive cyclovoltammograms of organic carbonyl containing BQ, AQ, TC and BZ-3 derivatives provided valuable information and comparison of the electrochemical reduction of the CO functional group in model molecules of different size, solubility and π-aryl aromaticity. Finally, potentialities for the electroanalytical measurement of BZ-3 at SPGEs via the room temperature ionic liquid [C6MIM][PF6] have been evaluated.
    RSC Advances 08/2012; 2(20):7735-7742. DOI:10.1039/C2RA20927F
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    ABSTRACT: The electrooxidation of the unsaturated propargyl alcohol has been explored on NiOOH electrodes in alkaline solution. Cyclic voltammetry, chronoamperometry and electrolyses were performed for the electrochemical response of propargyl alcohol. The identification and quantification of the final products from the electrolyses have been carried out. No evidence for the formation of propiolic acid has been found, however, a new product, (Z)-3-(2-propynoxy)-2-propenoic acid, was obtained. The stereochemistry of the product could be ascertained by 1H NMR spectroscopy. A tentative mechanism for the formation of (Z)-3-(2-propynoxy)-2-propenoic acid has been developed.
    Electrochemistry Communications 08/2012; 22:200–202. DOI:10.1016/j.elecom.2012.06.028
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    ABSTRACT: Myoglobin (Mb) is one of the most studied proteins and serves as model protein for evaluation and characterization the ligand–protein complexes such as the reversible binding of small molecules at the haem group. Nitration in proteins is a physiologically relevant process and the formation of 3-nitrotyrosine in vivo was first proposed as an in vivo marker of the production of reactive nitrogen species (RNS). We have performed the selectively nitration of Mb as model protein to carry out spectroscopic and electrochemical studies in order to add insights into the changes caused by nitration.The selection of the electrode, boron doped diamond (BDD), is critical as minimization of protein adsorption and retention of lytic activity is required to perform the electro-oxidative mononitration of Mb at Tyr103. Fig. 1 shows the voltammograms of the electrochemical reduction of native-Mb (solid line) at BDD electrode in sodium acetate buffer pH 4.0 in presence of saturated O2 conditions corresponds to the electrochemical reduction of MbFe (III) O2, which shows a slight decrease in the catalysis of O2 for NO2-Mb (dashed line).The study of the conformational and functional changes of the modified has been performed by the application of some spectroscopic techniques such as circular dichroism (CD), fluorescence, thermal stabilities and nuclear magnetic resonance. A relationship of thermal stability, structure and electrochemical behaviour of oxygen reduction has been observed for the electrosynthesis of the nitrated protein (NO2-Mb).
    Nitric Oxide 07/2012; 27:S37. DOI:10.1016/j.niox.2012.04.135
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    ABSTRACT: The electrochemical modification of residues in proteins [1] and other bioactive molecules offers the production of novel proteins, enzymes and other bioactive species, in comparison with traditional methodologies such as protein engineering and the use of chemical reagents. The results have important consequences for the labelling of proteins, specific immobilisation, and production of novel modified proteins for pathophysiology in diseases involving oxidative dysfunction [2]. Nitration in proteins is a physiologically relevant process and the formation of 3-nitrotyrosine in vivo was first proposed as an in vivo marker of the production of reactive nitrogen species (RNS).The electrosynthetic methodology was applied for the performance of selectively nitration of hen egg white lysozyme (HEWL) at tyrosines 20 and 23. We performed the electrosynthesis of the mononitration at Tyr23 and bisnitration at Tyr20 and Tyr23. Unmodified, mononitrated and bisnitrated lysozymes were used to study the role of nitration on the structure and thermostability in phosphate buffer conditions at pH 7.0. On one hand, we followed the change in structure of lysozymes by high field nuclear magnetic resonance (NMR) and circular dichroism (CD) spectroscopies. On the other hand, variations on the thermal stability were followed by CD and dynamic light scattering (DLLS). Finally, we performed lytic activities and computational molecular dynamics studies for comparison to our experimental data.
    Nitric Oxide 07/2012; 27:S37-S38. DOI:10.1016/j.niox.2012.04.136
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    ABSTRACT: The electrogeneration of ferrate (FeO42−) ion at a boron-doped diamond (BDD) anode from the oxidation of Fe3+ ion formed from Fe2+ ion as precursor in 0.1 mol dm−3 HClO4 has been studied by cyclic voltammetry and rotating disc electrode (RDE) voltammetry. The cyclic voltammograms showed that the anodic peak related to FeO42− ion generation, appearing just before water discharge with hydroxyl radical production, was controlled by a mixed process of diffusion and charge. The height of the corresponding RDE voltammetric wave was strongly inhibited with rising rotation speed. This anomalous behaviour was studied by scanning electrochemical microscopy (SECM), which confirmed that the electrogenerated FeO42− ion suffers a decomposition process to give Fe3+ and O2. From the SECM analysis, it was also found a clear inhibition effect on ferrate ion generation due to the presence of high Fe3+ concentrations in solution. The reactivity of the electrogenerated FeO42− ion for the removal of organic pollutants was assessed by treating the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) in 0.1 mol dm−3 HClO4 solution. Its direct oxidation at the BDD anode produced a slow disappearance of the herbicide. The destruction of 2,4-D was accelerated under the additional oxidative action of generated FeO42− ion, but yielding a low mineralization degree. HPLC measurements of the electrolyzed solutions revealed the formation of 2,4-dichlorophenol as aromatic by-product and maleic, malic, oxalic and formic acids as short chain carboxylic acids, most of which were formed more largely when FeO42− ion was generated.
    Electrochimica Acta 03/2012; 64:196–204. DOI:10.1016/j.electacta.2012.01.021
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    ABSTRACT: A frequently employed method for the diagnosis of electrochemical mechanisms is the Koutecky-Levich (KL) method. This method is based on the extrapolation of the reciprocal of the current intensity (or density) versus the reciprocal of the square root of the rotational rate of a rotating disc electrode (plot 1/j vs. omega(-1/2)). From the intercept and slope of this plot, several diffusional and kinetic parameters of the mechanism can be obtained. In this article, the relative error of j(k) (kinetic current density term) and of k(0) (standard rate constant) is estimated and discussed. Moreover, the relative error calculation is also estimated for the case when none of the kinetic terms in the KL expression (forward and backward reactions) can be disregarded.
    Electrochemistry Communications 02/2012; DOI:10.1016/j.elecom.2011.11.017
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    ABSTRACT: Bismuth-modified Pt nanoparticles supported on carbon have been employed as anode electrocatalyst for a direct formic acid fuel cell (DFAFC). Two different types of electrodes were used: a thin layer Pt/C working electrode deposited on a gold substrate and a coated catalyst (Pt/C) membrane. Bismuth was deposited on the Pt nanoparticles by irreversible adatom adsorption from a Bi3+ solution. Bi-modified thin-film working electrodes with different catalyst loadings (0.1, 0.5 and 1.0 mgPt cm−2) were tested for the electrooxidation of formic acid (2, 4.75 and 9 M formic acid solutions). Likewise, a Bi-modified coated catalyst membrane was used as anode in an air-breathing direct formic acid fuel cell. For this cell, polarization curves were obtained for different formic acid solutions. Independently of the type of electrodes, the presence of Bi caused a four/six fold increase of the electrooxidation currents as compared to unmodified Pt electrodes. Thus, the use of bismuth-modified carbon supported Pt nanoparticles is presented as an easy, feasible and versatile alternative for improving the efficiency of DFAFCs.
    Electrochimica Acta 02/2012; 63:105–111. DOI:10.1016/j.electacta.2011.12.076